The invention relates to a pressing die used for forging a heated blank, which in a pre-treatment operation has been given a volume essentially corresponding to that of the final product. The forging apparatus comprises upper and lower die parts arranged to be displaced towards each other and having contacting surfaces extending transversely of the direction of movement of the die parts, whereby when the contacting surfaces are pressed together and brought into contact with one another as a result of pressure exerted on said parts, the blank is shaped in conformity with a die cavity defined with precision by the die parts. The configuration of the thus forged component then essentially agrees with that of the desired finished component, i.e. no or at least only minimum post-treatment is required.
A device of the kind described above is previously known from U.S. Pat. No. 4,015,461. The forging apparatus described therein comprises two parts which are pressed against one another until the surfaces thereon that extend transversely of the direction of pressure exertion are brought into contact with one another. A die cavity having a carefully defined volume is thus defined, and the blank to be forged has been pre-treated so as to adopt that volume for the purpose of eliminating the need for post-treatments.
One problem encountered with this kind of forging dies is that during the forcing operation, material might be forced out from between the contacting surfaces, with the result that so called burrs may form on the component, making the undesired post-treatment necessary after all. At worst, the amount of material being expelled from between the contacting surfaces is of such a magnitude as making completion of the forging operation impossible.
Another problem encountered with forging dies of the kind outlined above is that they cannot be used for forging components having a more complex configuration, such as a cylinder having outwardly projecting fins or other protrusions thereon. It would be impossible to remove components of such a shape from a die of this kind.
It should be noted that by the expression xe2x80x9ccylinderxe2x80x9d as used in this context is intended a surface obtained by moving a straight line in parallel along a curve, such as an ellipse or a circle.
A first object of the present invention is to provide a forging apparatus, which is adapted satisfactorily to eliminate or to reduce to a minimum the need of post-treatment of the forged component.
A second object of the present invention is to provide a forging apparatus to be used to forge components having a more complex configuration.
A third object of the present invention is to provide a forging apparatus making an efficient manufacturing process possible.
The first one of these objects is achieved in accordance with the teachings of the invention in that such contacting surfaces that extend transversely of the direction of movement of the die parts and are mutually movable during the forging operation have no contact with the die cavity during the forging operation. This means that the material of the blank confined inside the die cavity during the forging operation cannot be squeezed out from between the contacting surfaces.
Furthermore, the forging apparatus preferably comprises a plurality of die members arranged to be displaced towards and away from the die cavity center and to be locked in their bought-together position in which they define the die cavity laterally. The fact that the members that define the die cavity radially, that is towards and away from the die cavity center, are arranged for radial movement means that during the forging operation the component is allowed to completely fill voids in the die members, and to thus form components having a comparatively complex shape. After the forging operation, the die members may be moved apart, thus allowing removal of the forged component.
Power-exerting means preferably are interconnected with the die members and arranged to move said members towards and away from the die center. Said power-exerting means are able to effect the pressing-together of the die members prior to the start of the forging operation, and to thereafter move said means apart after completion of the forging operation.
Preferably, the die members may be locked by a locking ring. The locking ring ensures even distribution of the radial pressure around the circumference of the entire die cavity in the course of the forging operation.
Preferably, the die parts may be displaced towards one another in a two-step operation, that is a first step, during which the locking ring is brought into contact with the die members, locking them in their brought-together position, and a second step, during which the blank is shaped in conformity with the die cavity, the configuration of which is precision defined by the die parts. This arrangement provides for a smooth forging process, wherein locking of the die cavity and the forging operation are effected in one and the same movement.
In accordance with a special embodiment of the die the die parts are arranged to be vertically spring-actuated. In consequence of this arrangement, the upper and the lower ends of the blank may be deformed simultaneously. This possibility is particularly advantageous for instance when fins or flanges are to be formed at the upper and the lower rim of the blank, or when multi-arm components, such as for instance cross members for universal joints are to be manufactured.
Other characterizing features of the invention will be apparent from the appended claims and will be described in the ensuring description of three presently preferred embodiments of the invention.